Automessage for Main Site Only?

Hi,

The instructions for Automessage say to Network Activate it. But we only want to use it on the main site...we don't want to give sub-site owners the ability to use it. I mean, we do want messages to go out to owners of all new sub-sites, but we don't want sub-site owners to see the plugin menu items or have the ability to set up their own auto-messages.

Is it okay to just activate it on the main site? I know this is probably a dumb question but I wanted to make sure there wasn't a specific reason for saying to Network Activate it.

Thanks,

Mark